The present invention relates to fusion and non-fusion spinal interbody devices.
Spinal interbody devices such as the Fernstrom ball developed by Dr. Ulf Fernstrom, the Harmon Spinal Sphere of the Austenal Company (New York, N.Y.) and the more recent Satellite Spinal System of Medtronic Sofamar Danek (Memphis, Tenn.) have attempted stabilization in a disc interspace with an insertable solid sphere. Because of the rigidity and lack of compression of such solid spheres, undesirable subsidence of the device may result leading to possible nerve agitation and further corrective surgery.
Nucleus propulsus replacement has also been attempted with non-rigid hydrogels, such as disclosed in U.S. Pat. No. 7,214,245 to Marcolongo et al. Such hydrogels, however, are prone to migration and escape from the interbody space.
Accordingly, a need exists for a compressible spinal interbody device that avoids the problems of interbody devices that are either too rigid or too yielding.